Ethan Clarke
Plastic is everywhere, from our television and computers to our cars and houses. However, not all plastics are the same. There are hundreds of different types of plastic, but they can be grouped into seven categories. These categories are numbered and each has its own unique properties. For example, LDPE is highly resistant to impact, moisture, and chemicals, making it ideal for everyday products such as bin bags, while PET is lightweight, strong, and typically transparent, making it perfect for food packaging and fabrics.
| Characteristics | Values |
|---|---|
| Definition | Synthetic or semisynthetic materials that use polymers as a main ingredient |
| Properties | Lightweight, durable, flexible, nontoxic, and inexpensive to produce |
| Production | 9.2 billion metric tons of plastic between 1950 and 2017, with more than half produced since 2004; 400 million metric tons produced in 2023 alone |
| Uses | Packaging materials, construction, textiles, consumer goods, transportation, electronics, machine parts, optics, healthcare, furniture, food packaging, home appliances, medical instruments |
| Environmental Impact | Polluting seas and land, contributing to climate change and air emissions, endangering wildlife and ecosystems |
| Recycling | Only about 9% of plastics ever produced have been recycled; HDPE and PET plastics have higher recycling rates |
| Incineration | Approximately 12% of plastics have been incinerated |
| Waste Management | About one-fifth of plastics are mismanaged, particularly in low-to-middle-income countries, leading to environmental leakage |
| Human Health Risks | Annual intake of microplastics by humans estimated at 70,000 to 120,000 particles, mainly through inhalation and food/drink |
| Alternatives | A 2024 study suggested that replacing plastics with alternatives may worsen greenhouse gas emissions in most cases |
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What You'll Learn
Plastic production
Plastic is a versatile material with thousands of polymer options, each with its own specific mechanical properties. It is a synthetic or semisynthetic material that uses polymers as its main ingredient. Its plasticity allows it to be moulded, extruded, or pressed into solid objects of various shapes.
Plastics are derived from natural gas, petroleum, and a small fraction from renewable materials such as polylactic acid. The production of plastics involves several processes, including compounding, moulding, and 3D printing. During compounding, different blends of materials are melt-blended to create formulations for plastics. This is typically done using an extruder, followed by pelletising the mixture. The pellets are then transformed into finished or semi-finished products through extrusion or moulding processes.
One common moulding technique is plastic injection moulding, where liquid plastic resin is injected into the empty cavity of a forming die, taking on its shape. Once the resin cools and solidifies, the die opens, and the finished part is ejected. This method is stable and reliable for high-volume production, accounting for over 80% of the common plastic items we use daily.
Another moulding process is blow moulding, where gas pressure is used to force molten resin into a mould cavity. This method is commonly used for transparent plastic drinking bottles, producing excellent surface quality. Thermoforming is another cost-effective process that uses simple equipment to mould plastic. It involves pre-heating a raw material, typically an elastomer or polyurethane, and placing it inside a die cavity. Heat and pressure are applied, causing the plastic to cure and take on its final form.
In recent years, 3D printing has emerged as an accessible method for creating plastic parts. Desktop 3D printing systems are affordable, require minimal space, and enable engineers, designers, and manufacturers to speed up production cycles. Various 3D printing technologies are available, such as fused deposition modelling (FDM), stereolithography (SLA), and selective laser sintering (SLS), each using different techniques to work with plastic.
The versatility and adaptability of plastics have led to their widespread use in various sectors, including packaging, construction, textiles, consumer goods, transportation, and electronics. However, the mismanagement of plastic waste, particularly in low- to middle-income countries, has resulted in significant environmental pollution, with an estimated one to two million tonnes of plastic entering our oceans annually.
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Plastic waste
The largest application of plastics is in packaging, constituting 50% of plastic waste. Single-use plastics alone account for 40% of annual plastic production. Other significant sectors utilising plastics include construction, textiles, consumer goods, transportation, electronics, and optics. The convenience and performance-enhancing additives in plastics have fostered a throw-away culture, exacerbating the waste problem.
Annually, an estimated 1 to 2 million tonnes of plastic enter our oceans, with previous estimates reaching 8 million tonnes. This waste originates primarily from middle-income countries, particularly in Asia. Rivers act as conveyor belts, carrying trash from land to sea, and once in the ocean, plastic waste breaks down into microplastics, spreading throughout the water column and reaching every corner of the globe.
Microplastics have been detected in municipal drinking water systems, the air we breathe, and even in human blood, lungs, and faeces. The full extent of the harm they inflict on human health remains uncertain, but it is a pressing question for scientists. Additionally, plastic pollution disrupts habitats and natural processes, impairing ecosystems' ability to adapt to climate change and affecting the livelihoods, food production, and social well-being of millions.
To address plastic waste, improved waste management systems, recycling, and product design are crucial. Reducing the production of unnecessary single-use plastics and investing in alternative materials with lower environmental impacts are also essential steps towards mitigating this global issue.
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Plastic recycling
The plastic recycling process typically begins with consumers sorting their plastic waste into recycling bins. Haulers then collect the plastic waste from these bins and take it to a material recovery facility (MRF). At the MRF, the plastic waste is sorted by size, shape, colour, and polymer type. Large cardboard, flat 2D paper materials, and 3D containers are separated using screens, while metals are sorted using magnetic and conductive properties. Glass is crushed and sifted, with only pieces larger than two inches continuing down the sort line.
Once the plastic waste has been sorted, it is melted and reformed into other items. This process can cause polymer degradation at the molecular level, and it requires careful sorting to avoid creating material with inconsistent properties. Mechanical recycling can also release microplastics into wastewater. An alternative to mechanical recycling is feedstock recycling, where waste plastic is converted into its starting chemicals, which can then be used to create fresh plastic. However, this process involves higher energy and capital costs.
Another challenge to plastic recycling is the economics of the process. Making new plastic is relatively cheap, while recycling plastic can cost as much as or more than the value of the recycled material. Despite these challenges, plastic recycling can have environmental and economic benefits. In 2022, over 5 billion pounds of plastic packaging were recycled in the U.S., driving job creation, revenue growth, reduced natural resource extraction, and reduced greenhouse gas emissions.
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Plastic pollution
Plastic waste that is not recycled, incinerated, or kept in sealed landfills becomes an environmental pollutant. One to two million tons of plastic enter our oceans each year, affecting wildlife and ecosystems. This plastic waste comes from rivers and landfills, ending up in the ocean. The probability that mismanaged plastic waste enters the ocean depends on factors such as the location and length of river systems, proximity to coastlines, terrain, and precipitation patterns. Rich countries produce the most plastic waste per person, but the mismanagement of waste in low-to-middle-income countries means that most ocean plastics come from these countries.
The production of plastics has increased nearly 230-fold over the last 70 years, with annual production reaching 460 million tons in 2019. Even if plastic production is reduced, improving waste management strategies is critical to ending plastic pollution. Domestic policies to improve waste management will be crucial, but richer countries can also contribute through foreign investments in waste management infrastructure in low-to-middle-income countries.
The environmental, social, and economic risks of plastics need to be addressed alongside other environmental stressors, such as climate change and ecosystem degradation. Plastic pollution can alter habitats and natural processes, reducing ecosystems' ability to adapt to climate change and affecting the livelihoods, food production capabilities, and social well-being of millions of people.
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Plastic alternatives
Plastic is a synthetic or semisynthetic material composed of polymers that can be moulded, extruded, or pressed into solid objects of various shapes. It is lightweight, durable, flexible, nontoxic, and inexpensive to produce, which has led to its widespread use. However, plastic waste that is not recycled, incinerated, or properly disposed of becomes an environmental pollutant, with one to two million tonnes of plastic entering our oceans each year. To address this issue, various alternatives to plastic are being explored, with a focus on reducing carbon emissions and environmental impact.
One alternative is to use reusable and refillable packaging or buy unpackaged products. This approach only requires a shift in consumer habits and behaviours. Another option is biodegradable algae-based packaging, which has gained attention due to its sustainability and ability to completely biodegrade in less than 47 days. Companies like B'zeos and Notpla have successfully developed edible drinking straws, condiment packets, cutlery, and plastic wrap from seaweed.
Additionally, there are compostable plastics, such as Vegware, that can break down in home compost heaps, although this process is very slow. Bioplastics, such as bio-PET, are also recyclable, but they are rarely recycled due to the lack of public collection facilities. Traditional alternatives to polyester and nylon clothing, which shed plastic microfibres during washing, include cotton, wool, linen, and hemp.
Other innovative solutions include a spray-on protective coating made from plant cellulose for produce and food items. This coating is designed to be rinsed off with water and degrade in soil within three days, potentially eliminating the need for plastic packaging. Natural fibres such as coconut fibre, hemp, husk, and cotton burs are also being explored as alternative packaging and shipping materials.
While there is no single magic solution to replace plastic, a varied range of alternatives is being developed and optimised for large-scale production. These alternatives aim to balance cost, sustainability, and functionality to address the environmental concerns associated with plastic waste.
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Frequently asked questions
There are technically thousands of different types of plastic, but they are grouped into seven categories.
The seven types of plastic are LDPE, PE, PET, HDPE, PVC, LDE, and PP.
LDPE stands for Low-Density Polyethylene. It was one of the first plastics to be produced and is highly resistant to impact, moisture, and chemicals. It is commonly used for everyday products like bin bags, thin-film packaging, and plastic bags.
PVC, or polyvinyl chloride, is known for its strength and durability. It is used in construction and pipes, as well as in plumbing products, electrical cable insulation, clothing, and medical tubing.
Some plastics that don't fit into the main categories include polycarbonate, acrylic, fibreglass, nylon, and polylactide. These plastics are harder to recycle due to their diverse chemical formulations.
